CA2467247A1 - Silane-crosslinked polyolefin coated fabrics for airbags - Google Patents

Silane-crosslinked polyolefin coated fabrics for airbags Download PDF

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Publication number
CA2467247A1
CA2467247A1 CA 2467247 CA2467247A CA2467247A1 CA 2467247 A1 CA2467247 A1 CA 2467247A1 CA 2467247 CA2467247 CA 2467247 CA 2467247 A CA2467247 A CA 2467247A CA 2467247 A1 CA2467247 A1 CA 2467247A1
Authority
CA
Canada
Prior art keywords
fabric
coated
grafted
crosslinked
olefin polymer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2467247
Other languages
French (fr)
Inventor
Stephen James
David Lawson
Stephen Lucas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dow Silicones Corp
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2467247A1 publication Critical patent/CA2467247A1/en
Abandoned legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00Layered products comprising a layer of synthetic resin
    • B32B27/12Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00Layered products comprising a layer of synthetic resin
    • B32B27/32Layered products comprising a layer of synthetic resin comprising polyolefins
    • DTEXTILES; PAPER
    • D06TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06NWALL, FLOOR, OR LIKE COVERING MATERIALS, e.g. LINOLEUM, OILCLOTH, ARTIFICIAL LEATHER, ROOFING FELT, CONSISTING OF A FIBROUS WEB COATED WITH A LAYER OF MACROMOLECULAR MATERIAL; FLEXIBLE SHEET MATERIAL NOT OTHERWISE PROVIDED FOR
    • D06N3/00Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof
    • D06N3/04Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof with macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D06N3/045Artificial leather, oilcloth or other material obtained by covering fibrous webs with macromolecular material, e.g. resins, rubber or derivatives thereof with macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds with polyolefin or polystyrene (co-)polymers
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60RVEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R21/00Arrangements or fittings on vehicles for protecting or preventing injuries to occupants or pedestrians in case of accidents or other traffic risks
    • B60R21/02Occupant safety arrangements or fittings, e.g. crash pads
    • B60R21/16Inflatable occupant restraints or confinements designed to inflate upon impact or impending impact, e.g. air bags
    • B60R21/23Inflatable members
    • B60R21/235Inflatable members characterised by their material
    • B60R2021/23504Inflatable members characterised by their material characterised by material
    • B60R2021/23509Fabric
    • B60R2021/23514Fabric coated fabric
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T442/00Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
    • Y10T442/20Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
    • Y10T442/2139Coating or impregnation specified as porous or permeable to a specific substance [e.g., water vapor, air, etc.]

Abstract

A fabric for use in air bags is coated with an olefin polymer crosslinked via grafted trialkoxy silane units. The silane units are crosslinked by hydrolysis and condensation of the alkoxysilane moieties.

Description

SILANE-CROSSLINKED POLYOLEFIN COATED FABRICS FOR AIRBAGS
FIELD OF THE INVENTION
[0001) The present invention relates to coated fabrics and to their production, and in particular to a coated fabric capable of maintaining a pressure barrier between two areas with a pressure differential. The invention also relates to air bags made with the coated fabrics.
BACKGROUND TO THE INVENTION
[0002) Coating compositions for textile substrates, which provide a flexible coat on the fabric, e.g. to decrease permeability of the fabric or to improve thermal protection of the fabric are well known in the art, and are described for example in EP-A-553840, WO01/12894, JP-A-6-227347 and EP-A-886164. Most of such coating compositions are based on silicone elastomers.
[0003] While fabrics coated with such compositions may be satisfactory for many air bag applications, they do not satisfy requirements where pressurised fluids are to be retained in a fabric envelope for a relatively long period. This requirement exists for example in the application of such coatings to side curtain air bags for the automotive industry. These side curtain air bags are intended to inflate at the time of impact, as do conventional air bags. The side curtains unfold to form a cushioned curtain between passengers and some of the side of the car body, e.g., the windows. As the intention is not merely to cushion the blow on impact itself, as is the case for conventional driver and passenger airbags, but e.g.
to protect passengers when a car is rolling, it is important that the side curtain air bag is sufficiently pressurised during such rolling process. Where conventional driver and passenger airbags only need to retain pressure for a fraction of a second, it is desirable that side curtain air bags maintain a suitable pressure for a few seconds. Similar applications exist where a pressurised fabric structure is desired to maintain a certain fluid pressure for a relatively extended period of time, e.g. in emergency chutes for aeroplanes, inflatable rafts etc.

DESCRIPTION OF THE INVENTION
[0004] A fabric according to the invention for use in air bags is coated with an olefin polymer crosslinked via grafted trialkoxysilane units which are crosslinked by hydrolysis and condensation of the alkoxysilane moieties.
[0005] The olefin polymer is preferably polyethylene, for example medium density polyethylene (MDPE) of density 0.935 to 0.955 g/mL or low density polyethylene (LDPE) of density 0.918 to 0.935 g/mL but can alternatively be an ethylene copolymer such as an ethylene vinyl acetate copolymer (EVA) containing for example 5 to 30% by weight vinyl acetate units or a copolymer of ethylene with up to 30% by weight of another olefin such as propylene, 1-butene or 1-hexene, or an ethylene propylene dime terpolymer containing up to S% by weight dime units.
[0006] The olefin polymer can be grafted with trialkoxysilane units by reaction with an alkenyl trialkoxy silane in the presence of a catalyst. The alkoxy groups of the trialkoxysilane preferably have 1 to 4 carbon atoms, particularly methoxy or ethoxy groups.
The preferred alkenyl group is vinyl although allyl and hexenyl are alternatives. One example of a preferred alkenyl trialkoxy silane is vinyl trimethoxy silane.
The grafting reaction can for example be carried out at elevated temperature in the presence of a peroxide catalyst such as benzoyl peroxide. The level of alkenyl trialkoxy silane grafted to the olefin polymer can for example be (0.2-20% by weight?). Suitable grafted polyethylenes are sold by AEI Compounds Limited of Gravesend, Kent, GB under the trade names SX700, and SX408.
[0007] The grafted polymer can contain a filler, preferably a reinforcing filler such as carbon black or silica, titania or glass microspheres. Suitable other fillers include ground quartz, ground cured silicone rubber particles and calcium carbonate. The amount of filler can for example be up to 25% by weight of the grafted polymer composition, but filler is preferably absent or present at no more than 5%. Other additional components may be included in the grafted polymer composition, for example dyes, adhesion promoters, colorants, pigments, viscosity modifiers or flexibilisers. Adhesion promoters include epoxy-functional or amino-functional organosilicon compounds or organotitanates.
[0008] The grafted polymer can be processed as a thermoplastic before being crosslinked. Crosslinking is brought about in a subsequent process by the action of moisture.
In the presence of moisture, the alkoxysilane groups are hydrolysed to silanol groups with a subsequent condensation reaction between silanol groups attached to different polymer molecules. The polymer composition preferably includes a condensation catalyst, for example a metallic or organometallic carboxylate such as dibutyltin dilaurate (DBTDL) or stannous octoate, preferably at 0.1-20% by weight based on the grafted polymer. The rate of crosslinking is determined by the rate of diffusion of moisture into the system and by the level of catalyst. It may be preferred to incorporate the catalyst at the final processing stage before crosslinking. Alternatively a grafted polymer composition containing catalyst can be sealed from moisture until it is coated on a fabric, at which point the large surface area to 1 S volume ratio allows rapid moisture diffusion and crosslinking.
[0009] The invention thus includes a process for producing a fabric for use in air bags, characterised in that the fabric is coated with an olefin polymer grafted with trialkoxy silane units and the grafted olefin polymer is subsequently crosslinked by hydrolysis and condensation of the alkoxysilane moieties.
[0010] In one preferred coating process, the fabric is coated by extrusion coating of the grafted olefin polymer. The polymer can for example be extruded through a slit die onto a fabric carried by a cooled backing roller. Alternatively the grafted olefin polymer can be coated on the fabric by laminating a heated film of the grafted olefin polymer to the fabric.
The fabric can for example be coated by a hot melt coating technique in which molten grafted olefin polymer is applied to a heated 2-roll mill, for example by extrusion, to form a film and the resulting film is laminated to the fabric at a nip. Another preferred coating process is hot melt coating, in which for example the grafted polymer composition is extruded onto the nip of rollers one of which has a less adhesive surface so that a polymer film is carried from the nip by the other roller and is contacted with the fabric at a subsequent nip on that roller.
Further alternative coating processes include spraying, gravure coating, bar coating, coating by knife-over-roller, coating by knife-over-air, padding and screen-printing.
The coating is preferably applied as a solventless, e.g. molten, composition, but can be dissolved in an organic solvent if desired.
S [0011] It is preferred that the composition is applied to a coat-weight prior to curing of at least 25 glm2. Preferably the coating thickness is from 25 to 150g/m2, more preferably 60 to 130g/m2 for applications where pressure needs to be maintained longer, e.g. in side curtain airbags, or 30 to 50 g/m2 for applications where the pressure retention is not so critical over prolonged periods, e.g. in standard driver airbags. Although it is not preferred, it is possible to apply the composition in multiple layers, which together have the thickness set out above. It is also possible to apply onto the coating composition a further coating, e.g. of a material providing low friction, or an additional textile fabric, whether woven or non-woven, to improve the strength and/or the feel of the fabric.
(0012] Preferred fabrics for use as substrate in the present invention may be made from synthetic fibres or blends of natural and synthetic fibres, and include polyamide, polyester, polyimide, polyethylene, polypropylene, polyester-cotton or glass fibre fabrics, most preferably polyamide fibres such as Nylon 6,6. They are preferably woven fabrics.
[0013] When the coated fabric of the invention is used to form air bags, the coating is preferably present on the surface of the air bag remote from the inflation source of the air bag, and optionally also on the surface of the air bag nearer the inflation source. If both sides of the fabric are coated, the total coating weight is preferably no more than 150 g/mz.
[0014] The crosslinked olefin polymer coating has a tear strength and elongation similar to that of silicone rubbers used commercially as air bag coatings, but has a substantially higher tensile strength, for example 50 to 100% higher. This has the advantage that the air bag coating does not fail by pinhole formation related to weakness of the coating film. Air bags coated according to the invention retain 0.5 bar pressure after 10 seconds inflation time, which is adequate pressure retention for side curtain air bags.
[0015] The invention is illustrated by the following Examples:

Example 1 [0016] A silane grafted polyethylene supplied by AEI Compounds, which is believed to be LDPE grafted with vinyl trimethoxy silane, was applied to fabric using a so-called hot melt coating technique. The coating material itself, when prepared and crosslinked in sheet form using 95% grafted polyethylene and S% DBTDL catalyst gave the following physical properties: - tear strength - 40kN/m; elongation at break - 650%; Shore A
hardness - 80;
tensile strength - 12 MPa.
[0017] The silane grafted polyethylene was extruded at 170oC onto a heated 2-roll mill and thereby coated onto both sides of a miniature inflatable curtain type airbag, itself prepared from a nylon-6, 6 woven fabric. The heated 2-roll mill was set at approx 170C to ensure formation of a suitable molten film required for the lamination process. The coating weight on the fabric was approximately 150 g/m2. The coated fabric was exposed to the atmosphere for a few days to initiate crosslinking of the methoxy silane sites, and the coated bags were subsequently deployed to test their pressure retention characteristics.
[0018] The coated miniature airbags thus produced from the hot melt coating trial were subjected to a cold gas inflation test that simulates the conditions to be experienced by the full size airbag. The bags retained 0.5 bar pressure after 10 seconds inflation time. There was partial delamination of the coating from the fabric in the inflation test;
these locations were the source of pressure leakage. If the fabric or coating composition is modified to increase adhesion, even better pressure retention can be expected.
Example 2 [0019] The grafted polyethylene composition of Example 1 was extrusion coated onto nylon-6, 6 woven fabric supported on a chilled roll. The polymer composition was extruded through a computer controlled slot die to give a coating weight of 40 g/m2 on the fabric. This trial produced a single sided coating onto plain fabric, hence no inflation testing was possible.
Again, adhesion was observed to be poor, but the feasibility of applying a thin film was proven. This coat weight yielded a very foldable, low friction material. Both these features are extremely important in the end application where the coated airbag needs to be tightly folded yet must deploy smoothly and rapidly without self adhering (blocking).

Claims (12)

1. A coated fabric for use in air bags, characterised in that the fabric is coated with an olefin polymer crosslinked via grafted trialkoxy silane units which are crosslinked by hydrolysis and condensation of the alkoxysilane moieties.
2. A coated fabric according to Claim 1, characterised in that the crosslinked olefin polymer is crosslinked polyethylene.
3. A coated fabric according to Claim 1 or Claim 2, characterised in that the grafted trialkoxy silane units are derived from an alkenyl trialkoxy silane.
4. A coated fabric according to Claim 3 characterised in that the alkenyl trialkoxy silane is vinyl trimethoxy silane.
5. An air bag formed of coated fabric, characterised in that the surface of the air bag remote from the inflation source of the air bag is coated with an olefin polymer crosslinked via grafted trialkoxy silane units which are crosslinked by hydrolysis and condensation of the alkoxysilane moieties.
6. Use of polyethylene crosslinked via grafted trialkoxy silane units which are crosslinked by hydrolysis and condensation of the alkoxysilane moieties as a coating for air bags.
7. A process for producing a fabric for use in air bags, characterised in that the fabric is coated with an olefin polymer grafted with trialkoxy silane units and the grafted olefin polymer is subsequently crosslinked by hydrolysis and condensation of the alkoxysilane moieties.
8. A process according to Claim 7, characterised in that the grafted trialkoxy silane units are derived from an alkenyl trialkoxy silane.
9. A process according to Claim 8 characterised in that the alkenyl trialkoxy silane is vinyl trimethoxy silane.
10. A process according to any of Claims 7 to 9 characterised in that the fabric is coated by extrusion coating of the grafted olefin polymer.
11. A process according to any of Claims 7 to 9 characterised in that the fabric is coated by lamination of a heated film of the grafted olefin polymer to the fabric.
12. A process according to Claim 11 characterised in that the fabric is coated by a hot melt coating technique in which molten grafted olefin polymer is applied to a heated 2-roll mill to form a film and the resulting film is laminated to the fabric
CA 2467247 2001-11-16 2002-11-11 Silane-crosslinked polyolefin coated fabrics for airbags Abandoned CA2467247A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0127472.9 2001-11-16
GB0127472A GB0127472D0 (en) 2001-11-16 2001-11-16 Coated fabrics
PCT/GB2002/005071 WO2003043817A1 (en) 2001-11-16 2002-11-11 Silane-crosslinked polyolefin coated fabrics for airbags

Publications (1)

Publication Number Publication Date
CA2467247A1 true CA2467247A1 (en) 2003-05-30

Family

ID=9925858

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 2467247 Abandoned CA2467247A1 (en) 2001-11-16 2002-11-11 Silane-crosslinked polyolefin coated fabrics for airbags

Country Status (11)

Country Link
US (1) US20050003722A1 (en)
EP (1) EP1444097B1 (en)
JP (1) JP3938570B2 (en)
KR (1) KR20050044469A (en)
AT (1) ATE294709T1 (en)
AU (1) AU2002341200A1 (en)
CA (1) CA2467247A1 (en)
DE (1) DE60204042T2 (en)
ES (1) ES2238608T3 (en)
GB (1) GB0127472D0 (en)
WO (1) WO2003043817A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0508155D0 (en) * 2005-04-22 2005-06-01 D S Smith Uk Ltd Method for forming laminated products
JP5221556B2 (en) * 2006-12-06 2013-06-26 ダウ・コーニング・コーポレイション Air bag and assembling method thereof
EP2500454B1 (en) * 2011-03-16 2015-05-13 Autoliv Development AB A fabric for use in the manufacture of an inflatable air-bag
JP6113674B2 (en) * 2014-02-13 2017-04-12 株式会社神戸製鋼所 Copper alloy strip with surface coating layer with excellent heat resistance

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1536562A (en) * 1975-02-13 1978-12-20 Bicc Ltd Manufacture of laminates including cross-linked polymers
JP3014127B2 (en) * 1990-08-16 2000-02-28 旭化成工業株式会社 Laminated fabric
JPH06227347A (en) * 1993-02-04 1994-08-16 Kuraray Co Ltd Air bag
EP0649936B1 (en) * 1993-10-21 1997-08-13 Milliken Research Corporation Fabric treated with polymer dispersion to reduce porosity
US6348543B1 (en) * 1999-06-17 2002-02-19 Milliken & Company Fabric coating compositions providing excellent resistance to seam combing, particularly for use on automotive airbag fabrics

Also Published As

Publication number Publication date
DE60204042T2 (en) 2006-01-19
JP3938570B2 (en) 2007-06-27
KR20050044469A (en) 2005-05-12
DE60204042D1 (en) 2005-06-09
EP1444097A1 (en) 2004-08-11
ES2238608T3 (en) 2005-09-01
WO2003043817A1 (en) 2003-05-30
GB0127472D0 (en) 2002-01-09
EP1444097B1 (en) 2005-05-04
US20050003722A1 (en) 2005-01-06
JP2005509759A (en) 2005-04-14
AU2002341200A1 (en) 2003-06-10
ATE294709T1 (en) 2005-05-15

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Legal Events

Date Code Title Description
EEER Examination request
FZDE Discontinued